1. Field of the Invention
The present invention relates to an air bag in a vehicle for protecting a passenger from a side collision. This air bag is arranged substantially in the vertical direction between a vehicular inner wall of an automobile and a passenger when the air bag is expanded.
2. Description of Related Art
Conventionally, an air bag for protecting a passenger from a side collision (hereinafter, abbreviated as side collision air bag or air bag) has been incorporated in a door panel or a seat in a folded state. The side collision air bag has been arranged between a vehicular inner wall of an automobile and a passenger when the air bag is expanded (refer to Japanese Unexamined Patent Publication Number JP-A-7-117610 and Japanese Unexamined Patent Publication Number JP-A-8-156668).
Further, when the chest area or vicinity head area of a passenger is to be protected, the side collision air bag is incorporated in a portion of a door panel or a seat rear the passenger's head in a folded state because door glass or the like is arranged rear of the head of the passenger and a folded air bag cannot be arranged there.
As a result, when expanded, the side collision air bag provides an expanded portion rear the passenger's chest and an expanded portion rear the passenger's head extended upwardly from the lower portion of the air bag. Further, the air bag is incorporated in a folded state at the lower side of an expanded state with the lower side in the expanded state as the upstream side of flow expansion gas which expands the bag.
However, according to such a side collision air bag, when the output of an inflator for supplying the expansion gas is small, the following problem occurs. When the chest of a passenger interferes with the lower side of the bag during expansion of the air bag (prior to completion of expansion), the expansion gas in the lower side of the air bag escapes to the upper side. As a result, a sufficient inner pressure cannot be ensured on the lower side of the air bag.
Accordingly, the inflator for supplying expansion gas to such a side collision air bag has a large output. Therefore, the weight of an air bag device for side collision is increased.